There’s a common definition of the word “obese”. We think of people who are really fat as being obese. I was one of them.
What is Obesity?
Obesity has a technical definition which is somewhat arbitrary. It is a function of weight and height and is known as BMI (Body Mass Index). The US government definition is (NCHS Data Brief ■ No. 288 ■ October 2017):
Obesity: BMI was calculated as weight in kilograms divided by height in meters squared, rounded to one decimal place.
Obesity in adults was defined as a BMI of greater than or equal to 30.
BMI Weaknesses as a Metric
BMI (and obesity) does not take into account body composition such as body fat or lean body mass. Two people can have the same BMI and be technically obese and one be solid muscle with little body fat and the other have significantly more body fat.
However, for the “average” person BMI is a decent measurement of fatness.
Obesity and Health
Generally, obesity and health are inversely related but there are people who are obese (by BMI) but are healthy. There are also people who are not obese but have poor health. This observation has led to the concept of personal fat threshold (PFT). This is described in (Taylor R, Holman RR. Normal weight individuals who develop type 2 diabetes: the personal fat threshold. Clin Sci (Lond). 2015 Apr;128(7):405-10) (PDF).
Personal Fat Threshold (PFT)
The Personal Fat Threshold concept is that there’s a level of fatness which the individual can tolerate before their health is impacted. This concept is tempting but has some problems.
PFT is not all that useful in the a-priori sense. There is no objective test to see if someone is at or near their PFT. Obesity isn’t useful as a metric. Neither is body fat level.
The only use of PFT is to support the medical advice to patients of weight loss as a tool for management of Type 2 diabetes. The PFT concept doesn’t actually contribute much since it has been believed (before the PFT concept was developed) that weight loss of about 15% resolves diabetes (Reversing Diabetes with Weight Loss: Stronger Evidence, Bigger Payoff).
Until there’s an a-priori means of measuring PFT the approach seems to be not all that useful. No medical doctor can tell you that you are 10 lbs away from your PFT. The point is completely hidden until it manifests. All it says that is if you are not technically considered to be obese and you are diabetic it is because you have gone over your personal fat threshold.
PFT – My Own Experience
There are three lines of reasoning from my own experience that call into question the PFT theory.
One was from my own experience with Insulin as a Type 2 Diabetic. I put on 40 lbs in a short time when I was put on Insulin. Conversely, when I got off Insulin my weight dropped quickly. Teenage females who are Type 1 diabetics and want to lose weight are well aware of this relationship. Weight increases followed Insulin increases (Skovsø S, Damgaard J, Fels JJ, Olsen GS, Wolf XA, Rolin B, Holst JJ. Effects of insulin therapy on weight gain and fat distribution in the HF/HS-STZ rat model of type 2 diabetes. Int J Obes (Lond). 2015 Oct;39(10):1531-8). not Insulin followed weight. Eventually, stasis is reached in weight and Insulin amount – at least in the short term.
Increasing dietary carbohydrates requires pumping more Insulin. When you stop eating dietary carbohydrates you don’t have to inject extra insulin for the meal.
The second reason was the increase in Insulin that is required over time to maintain blood sugar levels. I started at about 40g of Insulin and had good blood sugar controls. By four later my weight was stable but the amount of Insulin to keep blood sugar stable kept increasing to about 120 units. More particularly, the amount of insulin to cover carbohydrate loads increased. In my own case 1 unit of Insulin could cover 15 grams of carbs when I started Insulin and by four years later 1 unit wasn’t enough to cover 8 grams. All of this was at a stable weight (after the initial gain) and the same level of carbohydrates.
A third reason is my own weight history. I was at 285 lbs and non-diabetic for years. Then I mysteriously lost 50 lbs down to 235 lbs over the course of about six months. This is a common occurrence with Type 2 diabetics (Unexplained Weight Loss and Diabetes). After six months of this unexplained weight loss, I was then diagnosed with diabetes.
Perhaps this is the body pushing back from the PFT but it does call the concept into question – or at least indicate the real issue is much more complicated. After being put on Metformin my weight stabilized at around 10 lbs higher (although Metformin is said to lower weight). As my diabetes got worse my doctor tried different medications some of which added weight and some (like Byetta) caused small weight loss. Finally, the addition of Insulin added 40 lbs to my weight.
I did low carb while on Insulin but it only took my HbA1C down to 6.4. It wasn’t until I did low carb plus Intermittent Fasting that I was able to get off Insulin and my weight fell very quickly. My last HbA1C was 5.2 which is a normal non-diabetic number.
Carbohydrate Insulin Relationship
At the very least, if the PFT concept is salvageable, it needs to be modified for increasing Insulin Resistance levels. If the best treatment for diabetes is weight loss the best way for Type 2 Diabetics to lose weight is to reduce insulin levels. The best way to reduce insulin levels is to the insulin load of the diet. For a Type 2 Diabetic who is on Insulin this results in a loss of a lot of weight in a very short period of time.
The recommendation that losing 15% of body weight does not seem plausible to a diabetic like myself. I’ve lost more than 15% from my peak weight and not been able to control my diabetes. I lost weight with Low Carb by itself but not enough to get off Insulin. At it was more than 15% of weight loss. If I was told that losing 15% of my body weight would control my diabetes I would have told my doctor that I tried it and it didn’t work.
I lost much less than 15% of my weight in the beginning of Low Carb plus Intermittent Fasting and was able to get off Insulin completely. It was getting off Insulin which allowed me to lose weight. And it was reducing my body’s Insulin needs by the Low Carb diet and Intermittent Fasting which worked for me.